U.S. patent number 8,894,693 [Application Number 12/289,755] was granted by the patent office on 2014-11-25 for orthopaedic fixation component and method.
This patent grant is currently assigned to Ecole de Technologie Superieure, Valorisation Recherche HSCM, Limited Partnership. The grantee listed for this patent is Yan Bourgeois, Georges Yves Laflamme, Yvan Petit. Invention is credited to Yan Bourgeois, Georges Yves Laflamme, Yvan Petit.
United States Patent |
8,894,693 |
Petit , et al. |
November 25, 2014 |
Orthopaedic fixation component and method
Abstract
An orthopaedic fixation component attachable to a femur, said
femur defining a femur shaft, a femur head and a femur neck
extending therebetween, said femur further defining a greater
trochanter limiting laterally said femur neck, said orthopaedic
fixation component comprising: a shaft section fixation portion and
an end section fixation portion extending substantially
longitudinally therefrom, said shaft section and end section
fixation portions being respectively securable to said femur shaft
and said greater trochanter; said end section fixation portion
including a pair of end arms, said end arms being configured, sized
and positioned to delimit a trochanter receiving recess for
substantially fittingly receiving a prominent portion of said
greater trochanter.
Inventors: |
Petit; Yvan (St-Mathieu de
Beloeil, CA), Laflamme; Georges Yves (Montreal,
CA), Bourgeois; Yan (St-Mathieu de la Prairie,
CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Petit; Yvan
Laflamme; Georges Yves
Bourgeois; Yan |
St-Mathieu de Beloeil
Montreal
St-Mathieu de la Prairie |
N/A
N/A
N/A |
CA
CA
CA |
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Assignee: |
Valorisation Recherche HSCM,
Limited Partnership (Montreal, CA)
Ecole de Technologie Superieure (Montreal,
CA)
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Family
ID: |
41415456 |
Appl.
No.: |
12/289,755 |
Filed: |
November 3, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090312758 A1 |
Dec 17, 2009 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61129221 |
Jun 12, 2008 |
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Current U.S.
Class: |
606/280; 606/286;
606/74; 606/297; 606/70 |
Current CPC
Class: |
A61B
17/809 (20130101); A61B 17/74 (20130101); A61B
17/82 (20130101); A61B 2017/00867 (20130101); A61B
17/8061 (20130101) |
Current International
Class: |
A61B
17/80 (20060101); A61B 17/82 (20060101) |
Field of
Search: |
;606/280-299,74 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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WO 2008/019511 |
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Feb 2008 |
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WO |
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Primary Examiner: Schaper; Michael T
Parent Case Text
The present application claims priority from U.S. Provisional
Patent Application Ser. No. 61/129,221 filed on Jun. 12, 2008.
Claims
What is claimed is:
1. A fixation component securable to a femur, said femur defining a
femur shaft and a greater trochanter extending from said femur
shaft, said greater trochanter defining an anterior facet and a
lateral facet, said fixation component comprising: a shaft section
fixation portion, said shaft section fixation portion including a
substantially elongated shaft arm defining a shaft arm longitudinal
axis; and an end section fixation portion extending substantially
longitudinally from said shaft section fixation portion, said end
section fixation portion defining a pair of end arms extending
substantially away from said shaft fixation portion, each one of
said end arms defining a corresponding end arm outer edge and a
substantially transversely opposed end arm inner edge, said end arm
inner edges of said end arms together defining a trochanter
receiving recess extending therebetween, said trochanter receiving
recess being configured and sized for receiving at least a selected
portion of said greater trochanter, said selected portion of said
greater trochanter being a prominent portion of said greater
trochanter that protrudes from adjacent portions of said greater
trochanter, said end arms being configured, sized and positioned
such that said trochanter receiving recess substantially fittingly
receives said prominent portion of said greater trochanter; said
shaft section fixation portion and said end section fixation
portion being configured and sized so as to be respectively
securable to said femur shaft and to said greater trochanter;
wherein said end arms are configured, sized and positioned so as to
converge toward each other in a direction leading substantially
toward said shaft arm, said end arms together forming a
substantially V-shaped configuration, said V-shaped configuration
being laterally asymmetrical relative to said shaft arm
longitudinal axis, each of said end arms defining a corresponding
end arm proximal section and a substantially longitudinally opposed
end arm distal section, said end arm distal sections of said end
arms merging integrally with each other at a merging location; said
end arms being also configured, sized and positioned such that one
of said end arms is securable to said anterior facet and another
one of said end arms is securable to said lateral facet when said
fixation component is operatively secured to said greater
trochanter.
2. A fixation component as defined in claim 1, wherein said
fixation component has a generally asymmetrical substantially
"Y"-shaped configuration.
3. A fixation component as defined in claim 2, wherein said end
arms both extend integrally from said shaft arm.
4. A fixation component as defined in claim 3, wherein said shaft
arm and said end arms are rigidly secured to each other in a
substantially stable spatial relationship relative to each
other.
5. A fixation component as defined in claim 1, wherein said end arm
proximal sections each define a respective free end and said end
arms are disjoint from each other between said merging location and
said free ends.
6. A fixation component as defined in claim 5, wherein each of said
end arms define a substantially concave end arm inner surface and a
substantially convex end arm outer surface located substantially
opposed to said end arm inner surface, each of said end arms also
defining at least one end arm fastening aperture extending
therethrough between said end arm inner and outer surfaces, said at
least one end arm fastening apertures of said two arms being angled
relative to each other.
7. A fixation component as defined in claim 1 wherein said end arms
define an end arm midway axis extending midway between said end
arms, said end arm midway axis being angled relative to said shaft
arm longitudinal axis.
8. A fixation component as defined in claim 1, wherein said end
arms are configured, sized and positioned such that said end arms
inner edges substantially partially encircle said prominent portion
of said greater trochanter.
9. A fixation component as defined in claim 8, wherein said end arm
inner edges merge with each other substantially adjacent to said
shaft arm so as to form a nadir, said end arms being further
configured, sized and positioned such that said nadir is located
substantially underneath said prominent portion of said greater
trochanter when said fixation component is operatively mounted on
said femur.
10. A fixation component as defined in claim 1, wherein said end
arms are each provided with a respective end arm attachment for
attaching said end arms to said greater trochanter.
11. A fixation component as defined in claim 10, wherein said end
arm attachments each include at least one end arm fastening
aperture extending through a respective one of said end arms.
12. A fixation component as defined in claim 1, wherein at least
one of said end arms defines a substantially concave end arm inner
surface and a substantially convex end arm outer surface located
substantially opposed to said end arm inner surface.
13. A fixation component as defined in claim 1, wherein at least
one of said end arms tapers in a direction leading substantially
away from said shaft arm so as to define a substantially pointed
anchoring apex.
14. A fixation component as defined in claim 1, wherein said shaft
arm is provided with a shaft arm attachment for attaching said
shaft arm to said femur shaft.
15. A fixation component as defined in claim 14, wherein said shaft
arm attachment includes shaft arm attachment apertures for
receiving suitable attachment components.
16. A fixation component as defined in claim 15, wherein said shaft
arm defines a shaft arm flange extending substantially laterally
from the remainder of said shaft arm, at least one of said arm
attachment apertures extending through said shaft arm flange.
17. A fixation component as defined in claim 16, wherein said shaft
arm defines a plurality of shaft arm flanges each extending
integrally and substantially laterally from the remainder of said
shaft arm, at least one respective one of said arm attachment
apertures extending through each of said shaft arm flanges.
18. A fixation component as defined in claim 17, wherein said shaft
arm flanges are grouped in pairs with members of a given pair
extending in substantially laterally opposite and substantially
longitudinally offset relationships relative to each other.
19. A fixation component as defined in claim 17, wherein said shaft
arm attachment further includes cerclage cable channels extending
substantially transversely across said shaft arm for receiving
cerclage cables.
20. A fixation component as defined in claim 19, wherein a pair of
cerclage cable channels extends through said shaft arm proximally
to each pair of shaft arm flanges.
21. A fixation component as defined in claim 17, wherein at least a
subset of said shaft arm flanges extend generally in a lateral
plane, a projection of said V-shaped configuration in said lateral
plane being laterally asymmetrical relative to a projection of said
shaft arm longitudinal axis in said lateral plane.
22. A fixation component as defined in claim 1, wherein said
fixation component is provided with cerclage cables having a
portion thereof secured to said shaft arm.
Description
FIELD OF THE INVENTION
The present invention relates to the general field of orthopaedic
surgery components and methods and is particularly concerned with
an orthopaedic fixation component and method.
BACKGROUND
There exists a wide variety of situations wherein it is desirable
to fixate adjacent bone pieces or segments to promote healing of a
fracture. Such situations occur, for example, whenever a fragment
of the greater trochanteric portion of the femur bone needs to be
fixated to the shaft of the femur.
With the aging demographics of many industrialized countries, hip
related surgical procedures are becoming increasingly prevalent. An
example of such procedures is the so-called total hip replacement
surgery or arthroplasty which is typically performed as a
consequence of osteoarthritis of the hip joint. The procedure
involves replacing the diseased cartilage and bone of the hip joint
with artificial materials including an artificial prosthesis.
During the procedure, a segment of the greater trochanteric portion
of the femoral bone is typically temporarily osteotomized, that is
a the greater trochanter is surgically separated from the proximal
end of the femur so that the soft tissue attached to the greater
trochanter can be moved aside in preparation for implantation of
the femoral stem of the replacement prosthesis into the medullar
canal of the femoral shaft. Once the femoral stem of the prosthesis
is seated within the medullar canal in the femur, the greater
trochanter is re-attached to the proximal end of the femur.
The greater trochanter is subjected to considerable stress imparted
thereon by anatomical structures such as muscles attachments during
normal use of the hip. Accordingly, mechanical fixation of the
greater trochanter to the femoral shaft is mandatory in order to
promote healing of the fracture created by the osteotomizing step
of the hip replacement procedure or traumatic injury.
Also, because of the considerable stress imparted on the greater
trochanter as a consequence of the total hip arthroplasty
procedure, it is estimated that this type of procedure is
associated with a relatively high percentage of greater trochanter
post-surgical fractures, which, in turn, may require fixation.
Other examples of situations wherein fixation of the greater
trochanter to the femur shaft is required include trochanter and/or
proximal femur reconstruction, corrective or revision hip surgery
and the like.
One relatively common prior art method for fixating the greater
trochanter to the proximal femur shaft is a so-called "cerclage"
fixation technique wherein a flexible member, such as a cable, is
drawn tight and clamped in order to encircle the target fixation
site and to hold the bone portions together until they have time to
heal.
Typically, the surgical cables are implanted using tensioning
devices which apply tension to a surgical cable looped around the
bone. Crimps are then added and deformed to clamp the cable loop in
place.
The so-called "cerclage" methods, although somewhat useful, are
associated with a number of drawbacks. For example, such procedures
are typically considered relatively complex. Furthermore, cable
failure, migration or loosening may lead to fixation loss and
non-union of the bone fragments with clinical consequences such as
pain, lack of functionality and the like.
Other types of components have been devised in attempts to provide
solutions for fixating the greater trochanter to the femur shaft.
For example, some components include a bone grip for engaging over
the trochanter and a plate portion for extending down over the
shaft of the femur.
A well known typical example of such type of component is the
so-called "Cable-Ready" (a registered trade mark) greater
trochanteric re-attachment system developed by Zimmer. This system
involves the use of a component which has a substantially straight,
flat and elongated plate portion, integral with a hooked portion
terminating in a spike. Ideally, the hooked grip portion lies over
the greater trochanter, and the plate portion overlies the shaft of
the femur. Both portions have apertures to receive "cerclage"
cables, which are passed around the bone, to secure the device in
place.
Again, although somewhat useful, such devices also suffer from
numerous drawbacks. Indeed, as is well known, the greater
trochanter lies laterally, close to the skin, and can be easily
palpated on the lateral side of the thigh. Because it is the most
lateral point of the hip region, the greater trochanter may cause
discomforts when lateral pressure is exerted on the side of the
body such as when an individual lies on his or her side on a hard
surface. Most prior art fixation plates increase the discomfort by
being located over the most prominent portion of the greater
trochanter. Also, some prior art devices require that relatively
large incisions be performed in large leg muscles to position them
properly over the greater trochanter, with all the discomfort and
risk for complications associated with such operations.
Accordingly, there exists a need for an improved orthopaedic
fixation component and it is a general object of the present
invention to provide such an improved orthopaedic fixation
component.
SUMMARY OF THE INVENTION
In a broad aspect, the invention provides an orthopaedic fixation
component attachable to a femur, said femur defining a femur shaft,
a femur head and a femur neck extending therebetween, said femur
further defining a greater trochanter limiting laterally said femur
neck, said orthopaedic fixation component comprising: a shaft
section fixation portion and an end section fixation portion
extending substantially longitudinally therefrom, said shaft
section and end section fixation portions being respectively
securable to said femur shaft and said greater trochanter; said end
section fixation portion including a pair of end arms, said end
arms being configured, sized and positioned to delimit a trochanter
receiving recess for substantially fittingly receiving a prominent
portion of said greater trochanter.
The proposed orthopaedic fixation component is intended to be used
in particular with generally elongated bones such as the femur and
in particular for greater trochanteric re-attachment although other
applications are within the scope of the present invention.
The proposed orthopaedic fixation component provides a variety of
advantages for both the surgeon and the intended patient, some of
which are disclosed in greater details at the end of the detailed
description portion of the present application. In short, the
proposed orthopaedic fixation component is designed so as to
improve fixation while reducing post-operative complications.
The present invention also relates to a method of using an
orthopaedic fixation component in order to also improve fixation
while reducing post-operative complications.
Other objects, advantages and features of the present invention
will become more apparent upon reading of the following
non-restrictive description of preferred embodiments thereof, given
by way of example only with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the present invention will now be disclosed, by
way of example, in reference to the following drawings, in
which:
FIG. 1, in a perspective view, illustrates an orthopaedic fixation
component in accordance with an embodiment of the present invention
operatively mounted on a femoral bone, only a proximal portion of
which is shown;
FIG. 2, in a front view, illustrates the orthopaedic fixation
component and femoral bone shown in FIG. 1;
FIG. 3, in a perspective view similar to that of FIG. 1,
illustrates the insertion within the bone of some of the attachment
screws used with the orthopaedic fixation component in accordance
with the present invention;
FIG. 4a, in a transversal cross-sectional view taking along arrows
A-A of FIG. 3, illustrates the spatial relationship between the
inserted attachment screws shown in FIG. 3;
FIG. 4b, in a transversal cross-sectional view taking along arrows
B-B of FIG. 3, illustrates the spatial relationship between shaft
attachment screws shown in FIG. 3 and the stem of a replacement
prosthesis;
FIG. 5, in a top view, illustrates some of the features of the
proximal portion of the orthopaedic fixation component in FIGS. 1
through 4 when the latter is anchored to the femoral bone shown in
FIGS. 1 through 3;
FIG. 6, in a front view, illustrates the orthopaedic fixation
component shown in FIGS. 1 through 5;
FIG. 7, in a transversal cross-sectional view, illustrates the
cross-sectional configuration of an end arm, part of the
orthopaedic fixation component, the cross-section being taken
across line C-C of FIG. 6; and
FIG. 8, in a transversal cross-sectional view, illustrates the
cross-sectional configuration of an end arm, the cross-section
being taken along lines D-D of FIG. 6.
DETAILED DESCRIPTION
Referring to FIG. 1, there is shown, in a perspective view, a
fixation component in accordance with an embodiment of the present
invention, generally indicated by the reference numeral 10. The
fixation component 10 is shown, by way of example, mounted to a
femur generally indicated by reference numeral 12. It should,
however, be understood that the fixation component 10 is only shown
mounted to a femur 12 by way of example and that the fixation
component 10 could be used for fixating or securing bone segments
located at other anatomical regions without departing from the
present invention.
More specifically, the fixation component 10 is particularly well
adapted to be used at anatomical regions involving substantially
elongated bones defining a corresponding bone end region. By way of
non limitative examples, the fixation component 10 could, for
example, be used in applications involving the distal femur, the
proximal tibia as well as the proximal and distal humerus
regions.
As is well known, the femur 12 is an elongated bone. As shown in
FIGS. 1 through 3, the femur 12 includes a body or shaft 14
defining a pair of longitudinally opposed extremities or ends (only
the proximal one of which is shown in the Figures). The body or
shaft 14 of the femur is slightly bowed inferiorly and is narrowest
at its mid-point. Its middle two quarters are approximately
circular in transverse section. The distal end (not shown) of the
femur shaft 14 is broadened by medial and lateral condyles where it
articulates with the tibia and patella to form the knee joint.
The proximal end, shown in FIG. 1, includes a femur head 16, a
femur neck 18, a greater trochanter 20 and a lesser trochanter 22.
As is also well known, the femur head 16 is typically smooth and
forms 2/3 of a sphere. It is directed medially, superiorly, and
slightly inferiorly to fit into the acetabulum of the hip bone (not
shown).
The femur neck 18 connects the femur head 16 to the femur body or
shaft 14, typically at an angle of approximately 125 degrees. The
femur neck 18 is limited laterally by the greater trochanter 20 and
is narrowest in diameter at its mid-section. A broad, rough
inter-trochanteric line runs infero-medially from the greater
trochanter. This inter-trochanteric line passes inferior to the
lesser trochanter and becomes continuous with the spiral line on
the posterior aspect of the femur.
The inter-trochanteric line is produced by the attachment of the
massive illio-femoral ligament (not shown). The inter-trochanteric
line separates the interior surface of the femur neck 18 from the
femur body or shaft 14 of the femur 12. A prominent ridge, the
inter-trochanteric crest, unites the two trochanters 20, 22
posteriorly.
In the anatomical position, a line joining the tips of the greater
trochanters 20 normally passes through the center of the femur
heads 16 (only on of which is shown) and the pubic tubercies (not
shown). As shown more specifically in FIG. 2, the greater
trochanter 20 of the femur 12 is a substantially large, somewhat
rectangular projection from the junction of the femur neck 18 and
the femur body 14. It provides an attachment for several muscles of
the gluteal region. Some of these muscular attachments are
illustrated schematically in FIG. 1.
As is well known, both the gluteus medius and the gluteus minimus
are used for abduction and medial rotation of the thigh as well as
to steady the pelvis. The distal attachment of the gluteus medius
is typically located on the lateral surface of the greater
trochanter 20 while the distal attachment of the gluteus minimus is
typically located on the anterior surface of the greater trochanter
20.
The obturator internus and the gemelli, superior and inferior, are
used for laterally rotating the extended thigh and abducting the
flexed thigh. They are also used to steady the femur head 16 in the
acetabulum (not shown). Both the obturator internus and the gemini
superior and inferior have their distal attachment on the medial
surface of the greater trochanter 20.
Another muscle having its distal attachment on the greater
trochanter 20 is the piriformis muscle attached to the superior
border of the greater trochanter 20. It should be understood that
the muscular insertions illustrated in FIG. 1 are rough schematic
representations of the three major muscle groups hereinafter
discussed and should only be considered an approximation of the
actual anatomical reality.
Referring now more specifically to FIG. 6, there is shown in
greater details some of the features of the fixation component 10.
In general terms, the fixation component 10 includes a shaft
section fixation portion 24 and a substantially longitudinally and
integrally extending end section fixation portion 26 for being
respectively secured to a corresponding shaft section and a
corresponding end section of bone such as the femur shaft 14 and
the greater trochanter 20 shown in FIG. 1 through 3.
In the preferred embodiment, the fixation component 10 has a
generally asymmetrical "Y"-shaped configuration defining a shaft
arm generally indicated by the reference numeral 28 attached to a
pair of end arms generally indicated by the reference numerals 30
and 32.
The end arms 30, 32 typically extend integrally from the shaft arm
28 although they may be permanently or reversibly attached to the
latter without departing from the scope of the present invention.
Also, in the embodiment shown throughout the Figures, the shaft arm
28 and the end arms 30, 32 are rigidly secured to each other in a
substantially stable spatial relationship relative to each
other.
However, in other embodiments of the invention (not shown) the
shaft arm 28 and the end arms 30, 32 could be pivotally, slidably
or otherwise movably connected to each other so as to allow for
selective spatial movement therebetween in predetermined
combinations. For example, both end arms 30, 32 could be fixedly
secured to each other while being movably secured to the shaft arm
28. Alternatively, the end arms 30, 32 could be movable relative to
each other.
In instances wherein the shaft arm 28 and/or the end arms 30, 32
are movable relative to each other, the fixation component 10 may
further be provided with arm movement preventing means for either
permanently or releasably selectively preventing the relative
movements between the shaft arm 28 and one or both of the end arms
30, 32.
The end arms 30, 32 are typically configured, sized and positioned
so as to diverge away from each other, together forming a
substantially asymmetrical V-shaped configuration. Each one of the
end arms 30, 32 has a substantially elongated configuration
defining a corresponding end arm proximal section 34 and a
longitudinally opposed end arm distal section 36. Typically, the
end arm distal sections 36 of each end arm 30, 32 merge integrally
with each other.
Each one of the end arms 30, 32 also defines a corresponding end
arm outer edge 38 and a substantially transversely opposed end arm
inner edge 40. The end arm inner edges 40 together define a
trochanter receiving recess 42 extending therebetween for receiving
at least a selected portion of the greater trochanter 20. The
selected portion of the greater trochanter 20 adapted to be
received within the trochanter receiving recess 42 is typically a
particularly prominent or protruding portion 44 (seen in FIG. 1) of
the greater trochanter 20.
One of the main features of the present invention resides in that
the end arms 30, 32 are configured, sized and positioned such that
the trochanter receiving recess 42 substantially fittingly receives
the prominent portion 44 of the greater trochanter 20. More
specifically, the end arms 30, 32 are configured, sized and
positioned such that the opposed end arms inner edges 40
substantially partially encircle the prominent portion 44 of the
greater trochanter 20.
The end arm inner edges 40 typically merge with each other about
their respective end arm distal sections 36 so as to form a nadir
46. The end arms 30, 32 are typically further configured, sized and
positioned such that the nadir 46 is located substantially
underneath the prominent portion 44 of the trochanter 20 when the
fixation component 10 is operatively mounted on the femur 12.
Another feature of the present invention resides in that the end
arms 30, 32 are configured, sized and positioned relative to each
other so as to optimize the retaining action exerted thereby on the
greater trochanter 20 so as to prevent relative movement between
trochanteric portions and lessen the probability of creating a
secondary fracture.
The end arms 30, 32 provide a multi-directional holding action
adapted to cancel out the tendency of the three major muscles of
which the distal insertion is shown in FIG. 1 tending to exert a
pulling action upon the greater trochanter 20 along multiple
vectorial directions. This holding action prevents the trochanteric
portions from being pulled in any one of the vectorial directions
and, in particular, any one of the three major directions
illustrated in FIG. 1. The specific configuration, size and
position of the end arms 30, 32 is also adapted to take into
account that there is an intense and strong pull, particularly of
the abductor muscles of the hip during normal activities of daily
living such as ambulation.
The end arms 30, 32 are each provided with an end arm attachment
means for attaching or anchoring the end arms 30, 32 to the greater
trochanter 20. In the preferred embodiment, the end arm attachment
means includes at least one and preferably two end arm fastening
apertures 48 extending through corresponding end arms 30 or 32.
Each end arm fastening aperture 48 is adapted to receive a
corresponding fastening component such as an end arm bone screw 50
(seen for example in FIG. 1). Typically, each end arm fastening
aperture 48 has a substantially countersunk portion. Typically,
although by no means exclusively, the end arm bone screws 50 are of
the self-locking type. Self-locking type screws are typically
preferred, at least in part, because of the relatively thin layer
of the cortex of the bone in the regions of the greater trochanter
20.
As illustrated more specifically in FIG. 3 through 5, the
configuration, size and position of the end arms 30, 32 and their
corresponding end arm fastening apertures 48 is such that the end
arm bone screws 50 provide an entrapment effect for further
preventing trochanteric portions from being fractured or pulled out
by various forces acting thereon.
The configuration, size and position of the end arms 30, 32 is also
chosen in order to take into consideration the position of the
insertion of the main muscle attachments on the greater trochanter
20.
Referring back to the schematically illustrated muscular insertions
of FIG. 1, it can be seen, the end arms 30, 32 are configured,
sized and positioned so that their respective inner and outer
peripheral edges 40, 38 substantially clear these muscular
attachments or, at least, minimally interfere therewith so as to
reduce the risks of clinical problems once the fixation component
10 is operationally attached to the femur 12 and also so as to
facilitate the anchoring of the fixation component 10 to the femur
12 during surgery.
As shown more specifically in FIG. 6, the end arms 30, 32,
typically diverge away from each other in a proximal direction so
as to define an end arm angle "A" therebetween, Typically, although
by no means exclusively, the end arm angle "A" has a value of
between 60 and 120 degrees.
Another feature of the present invention resides in the
cross-sectional configuration of at least one and preferably both
end arms 30, 32. As illustrated more specifically in FIGS. 7 and 8,
each end arm 30, 32 preferably has a substantially concave end arm
inner surface 51 and a substantially convex end arm outer surface
52. Also, each of the end arms 30, 32 is also provided with
substantially rounded end arm inner and outer edges 40, 38.
The substantially concave end arm inner surface 51 is typically
variable along the length of the end arms 30, 32 and adapted to
allow for an improved contact engagement between the end arm inner
surfaces 51 and the substantially convex outer surface of the
greater trochanter 20.
The substantially arc-shaped cross-sectional profile of the end
arms 30, 32 is also adapted to increase the structural strength
thereof and, hence, allow for minimization of the overall thickness
of the end arms 30, 32 for a given material and considering given
auxiliary geometrical variables. The optimized fit between the
contact surfaces of the end arm inner surface 51 and the outer
surface of the greater trochanter 20 combined with the relatively
small cross-sectional distance between the end arm inner and outer
surfaces 51, 52 is adapted to provide greater comfort to the
patient with reduced risks of clinical complications.
As illustrated more specifically in FIGS. 1 through 5, the end arm
proximal portion 34 of at least one and typically both end arms 30,
32 typically curves inwardly so as to substantially override at
least a portion of the greater trochanter 20 and in operational
position provide a retaining means against axial displacement of
portions thereof.
Also, at least one and preferably both of the end arms 30, 32
typically taper proximally so as to define a corresponding
substantially pointed anchoring apex 53. Typically, the pointed
apex 53 is adapted to be inserted into the cortical portion of the
upper portion of the greater trochanter 20. Typically, although by
no means exclusively, the distance D between the apex 53 and the
nadir 46 has a value of between 40 and 70 millimeters.
Alternatively, in an embodiment of the invention not shown, the end
arm proximal portion 34 of at least one of the end arms 30, 32
could be deprived of a pointed apex 53 and/or made out of a
substantially deformable material so as to allow the surgeon to
bend the latter to a suitable shape for increasing the retention
characteristics thereof.
Referring back to FIGS. 1 through 3 and 6, there is shown that the
shaft arm 28 typically has a substantially elongated configuration
defining a shaft arm longitudinal axis 55 (shown in FIG. 6).
Another feature of the present invention resides in that the
substantially V-shaped configuration formed by the end arms 30, 32
is preferably substantially or laterally offset relative to the
shaft arm longitudinal axis 55.
Since the main muscular attachments to the greater trochanter 20
are located substantially anteriorly, the end arms 30, 32 are
typically offset substantially posteriorly relative to the shaft
arm longitudinal axis 55 so as to reduce the risk of interference
or obstruction with the muscles attached to the greater trochanter
20. Typically, as illustrated throughout the Figures, the end arm
32 being operatively mounted more anteriorly than the end arm 30,
the end arm 32 is positioned so as to extend at lesser angle
relative to the shaft longitudinal axis 55 than the end arm 30.
The shaft arm 28 is provided with a suitable shaft arm attachment
means for attaching the shaft arm 28 to the femur shaft 14. In the
embodiment shown throughout the Figures, the shaft arm attachment
means includes shaft arm attachment apertures 54 for receiving
suitable attachment components such as shaft arm screws 56 (seen
for example in FIG. 1). The shaft arm attachment apertures 54 are
typically provided with a countersunk section.
Each shaft arms attachment aperture 54 typically extends through a
corresponding shaft arm flange or tab 58 extending integrally and
substantially laterally from the shaft arm 28, The shaft arm
flanges or tabs 58 and their corresponding shaft arm attachment
apertures 54 are positioned in an offset relationship relative to
each other so as to prevent the shaft arm screws 56 from
interfering with each other when the fixation component 10 is
operatively mounted.
Typically, the shaft arm tabs 58 and corresponding shaft arm
attachment apertures 54 are grouped in pairs with members of a
given pair extending in laterally opposite and longitudinally
offset relationships relative to each other.
As illustrated more specifically in FIG. 4b, the shaft arm
attachment apertures 54 are positioned so as to no only provide
sufficient clearance between the shaft arm screws 56 but also to so
as to reduce the risks of interference with the femoral stem 60 of
a hip replacement prosthesis when the fixation component 10 is used
on a femur 12 having such a prosthesis.
The shaft arm attachment means typically further includes
"cerclage" cable channels 66 extending substantially transversely
across the shaft arm 28 for receiving "cerclage" cables 68.
Typically, although by no means exclusively, a pair of cerclage
cable channels 66 extends through the shaft arm 28 proximally to
each pair of shaft arm attachment apertures 54.
The fixation component 10 could be provided with "cerclage" cables
68 already having a portion thereof secured to the shaft arm 28 or
be simply adapted to receive conventional "cerclage" cables such as
the Zimmer Co--Cr cables.
Alternatively, the fixation component 10 could be provided with or
used in conjunction with a "cerclage" cable 68 made out of a
super-elastic material. Preferably, although by no means
exclusively, the super-elastic "cerclage" cable could be of the
type having a braided tuberous structure. Such a cable is described
in the PCT application bearing Serial No. PCT/CA2005/001859, naming
Brailovski et al as inventors, the entire content of which is
expressly incorporated herein by reference thereto.
Super-elastic cables having a braided tuberous structure provide a
synergistic advantage when used with the hereinabove disclosed
fixation component 10 by reducing the contact pressure on connected
bones and maintaining compression between fragments during the
fracture healing period.
In use, the specific configuration and size of the various sections
of the fixation component 10 allows a surgeon to position the
fixation component 10 on the femur 12 of an intended patient in
such a manner that the end arms 30, 32 are strategically positioned
to reduce the risk of having portions or fragments of the greater
trochanter 20 being displaced or pulled out of alignment relative
to their optimal anatomical relationship with the femur shaft
14.
The configuration, size and relative position of the end arms 30,
32 relative to the shaft arm 28 take into consideration both the
orientation and magnitude of the forces exerted by the muscles
attached to the greater trochanter 20 and the insertion location of
such muscles in, order to reduce the risk of interference
therewith.
The retaining action exerted by the end arms 30, 32 on portions or
fragments of the greater trochanter 20 is compounded by the
strategic location of end arm fastening apertures 48 adapted to
receive self-locking bone screws oriented to provide an entrapment
effect.
Furthermore, the configuration of the fixation component 10 is
designed in such a manner that the outward radial protrusion of the
end arms 30, 32 away from the greater trochanter 20 is also
minimized. Indeed, as mentioned previously, the end arms 30, 32 are
configured, sized and positioned relative to the shaft arm 28 in
such a manner that they create a trochanter receiving recess
therebetween, the trochanter receiving recess 42 being, in turn,
configured and sized for substantially fittingly circumventing the
prominent portion 44 of the greater trochanter 20.
Also, as mentioned previously, the configuration of the end arms
30, 32, including their cross-sectional configuration, is such that
the fit with the surface of the greater trochanter 20 is optimized
and the structural characteristics of the end arms 30, 32 is
improved, allowing for a thinner structure. The avoidance of the
prominent portion 44 of the greater trochanter 20 synergistically
combined with the improved contact with the greater trochanter 20
and the relatively thin profile reduces the protrusion of the end
arms 30, 32 from the femur 12 translates not only into an improved
aesthetical appearance but also a greater comfort for the
patient.
The shaft arm attachment means provided with the fixation component
10 allows the latter to be used with a wide variety of patients
including patients requiring total hip arthroplasty prosthesis.
Indeed, the strategic positioning of the shaft arm attachment
apertures 54 allows for a suitable number of shaft arm screws 56 to
be used in order to solidly anchor the shaft arm 28 to the femur
shaft 14 while reducing the risk of interference of the shaft arm
screws 56 not only with adjacent shaft arm screws 56 but also with
the femoral stem 60 of a hip replacement prosthesis inserted within
the medullary canal of the femur 12 such as shown in FIG. 4b.
Furthermore, the "cerclage" cable channels 66 allow for the use of
either conventional "cerclage" cables 68 or so-called super-elastic
cables 68. The use of super-elastic cables 68 and, in particular,
super-elastic cables 68 having a braided tubular structure provides
a synergistic effect when combined with the other features of the
fixation component 10.
By reducing the contact pressure on contacted bones, these cables
68 allow for the fixation component 10 to be used with patients
having particularly fragile bone structures. Also, such cables 68
are adapted to maintain a compression force between fragments
during the fracture healing period which is particularly crucial
with such patients.
Furthermore, the positioning of the "cerclage" cable channels 66 in
an alternating fashion with pairs of shaft arm attachment apertures
54 provides an optimal distribution of force exerted on the bone
structure for obtaining secure anchorage while reducing the risk of
traumatizing the femur shaft 14.
The present invention also relates to a method of using an
orthopaedic fixation component such as the hereinabove disclosed
fixation component 10 or other suitable fixation components. The
orthopaedic method, in accordance with the present invention,
includes positioning a fixation component to a bone structure
defining a bone shaft and a bone end section having a prominent
region in such a manner that the fixation component substantially
avoids the prominent section while providing an efficient retaining
action for preventing relative displacement between the bone
structures.
The proposed orthopaedic method also includes as an independent or
combined step the use of a "cerclage" cable made out of a
super-elastic material for attaching the fixation component to the
bone. Preferably, the step of using a "cerclage" cable includes
using a super-elastic "cerclage" cable having a braided structure
for attaching the fixation component to the bone structure.
Although the present invention has been described hereinabove by
way of preferred embodiments thereof, it can be modified, without
departing from the spirit and nature of the subject invention as
defined in the appended claims.
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